Energy collecting system and method of operating the same

ABSTRACT

In the air-conditioning system, a primary side to generate heat includes a heat storage and a heat source and produces cool or warm water using an inexpensive commercial power source such as a nighttime power source. A system collaboration unit is disposed between a motor to drive a water pump and a power source. The unit is connected to the motor via a cable. An output from the inverter is connected to the motor via a cable.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an energy collecting system anda method of operating the same in which energy is collected throughgeneration of electric power by a waterwheel using water used by, forexample, an air-conditioning load or the like in a building.

[0002] For example, as an air-conditioning system in a building, therehas been widely employed an air-conditioning system of heat storage typein which a heat source is operated using inexpensive nighttime electricpower to store generated heat in a heat storage. In the daytime in whichair-conditioning load takes place, the stored heat is fed from the heatstorage to the load, i.e., an air conditioner to achieveair-conditioning operation.

[0003]FIG. 12 is a diagram showing a configuration of an example of theprior art, namely, an open-loop air-conditioning system of heat storagetype. In a primary-side system S₁, the configuration includes a waterpump 1 which feeds water from a heat storage 16 to supply the water viaa water supply pipe 4 a to a heat source 4 and a both-end motor 2 ofwhich one shaft end is directly coupled with the water pump using ashaft coupling to drive the water pump. The other shaft end is coupledwith a waterwheel 12 via a clutch 12 b. The waterwheel is disposed at aposition at which potential energy of water discharged from the heatsource can be completely collected. Numerals 18 and 19 indicate electricpower sources, numeral 5 is a two-way valve to adjust a quantity of heatgenerated by the heat source, numeral 6 a is a water supply pipeconnecting the heat source to the waterwheel, and numeral 6 is anexpansion tank associated with the water supply pipe. The tank 6 breaksa siphon to apply a head of the supplied water (potential energythereof) to the waterwheel. In place of the expansion tank, a vacuumbreaking valve may be disposed depending on cases. Numeral 12 cindicates a water supply pipe to return the water from the waterwheel tothe heat storage. That is, the water supplied to the heat source 4 bythe water pump 1 is heated by the heat source and is then fed to thewaterwheel 12. The waterwheel 12 is operated by the potential energy ofthe water to generate power and then imparts the power to the both-endmotor 2. The load of the motor becomes lower than that of the waterpump, the discrepancy therebetween corresponds to the power impartedfrom the waterwheel. The water from the waterwheel then returns to theheat storage.

[0004] The secondary-side system S₂ is a load of an air conditioner orthe like and supplies water from the heat storage 16 via a water supplypipe 7 a to an air han (air handling unit) 8 and a fan coil 9 by a pump7. The air han 8 includes an adjusting valve 8 a to adjust a quantity ofheat. The fan coil 9 also includes a similar adjusting valve 9 a. Thewater of which heat is radiated is returned via the water supply pipe 7b to the heat storage 16.

[0005]FIG. 13 shows an operating characteristic graph of a pump and awaterwheel in an example of the prior art. A total water pumping-upprocess of the pump, an effective head of the waterwheel, and power ofthe pump and the waterwheel are indicated along an ordinate. A waterflow rate is indicated along an abscissa. A curve A is a curve of Q,Hperformance of the pump and a curve C is a curve of shaft power when thewaterwheel is not operated. The total water pumping-up process isrequired to operate only the water pump to supply water at a flow rateof Q0 to the water supply system shown in FIG. 9. The operation point inthis operation is point O4 on the curve A. Power consumed in thisoperation is L1 indicated by pump shaft power, and the operation pointis point O1 on the curve C. A curve B indicates an effective head of thewaterwheel (pressure head difference between the inlet and the outlet ofthe waterwheel). This means that when water flows at a flow rate of Q0,a pressure head difference (effective head) of H1 occurs between theinlet and the outlet of the waterwheel, and this potential energy isabsorbed to generate power as below.

[0006] A curve D is a power curve when the water pump and the waterwheelare operated. Power consumed in the operation is L2 indicated by pumpshaft power and the operation point is point O2 on the curve D. That is,when the flow rate is Q0, power generated by the waterwheel is L3.

[0007] In this case, the power collection ratio (L3/L1) is about 20% toabout 30%.

[0008] In this way, the conventional apparatus effectively usespotential energy of the pumped-up water passed through the heat source.

[0009] For example, JP-A-50-128801 (a power collection pumping machine)and JP-A-50-49701 (a power collection pumping machine) describes knownexamples of this apparatus. However, the prior art technique uses aclutch to directly couple a motor with a waterwheel and there is aproblem of improvement of transfer efficiency of the clutch. Thereexists another problem. That is, the energy collected by the waterwheelis power and there is a problem that the power cannot be used in thiscase, in consideration of structure, for any other load in the building.JP-A-5-10245 (an electric power generator using waterwheel ofpaddle-wheel type) is a known example of waterwheel electric powergeneration using a waterwheel in a dam, a paddy field, or a watercourse.

SUMMARY OF THE INVENTION

[0010] It is therefore an object of the present invention to collectunused energy in a building by waterwheel electric power generation touse the energy again.

[0011] According to the present invention, there is provided an energycollecting system comprising as basic units a heat storage disposed in alower section of a building; a heat source disposed in an upper sectionof the building for imparting heat to water supplied from the heatstorage by electric power from a commercial power source and therebyproducing cool or warm water; a primary cool/warm water pump for pumpingup the water from the heat storage and supplying the water via a suckingpipe to the heat source; a water supply pipe disposed between adischarge outlet of the primary cool/warm water pump and the heatsource; a water supply pipe for returning water from a discharge outletof the heat source to the heat storage; an expansion tank or a vacuumbreaking valve disposed in a highest section of the water supply pipe; awaterwheel disposed in a lowest section of the water supply pipe forcollecting potential energy of the water discharged from the heatsource; an electric power generator rotated by torque generated by thewaterwheel to generate electric power; an inverter connected to anoutput port of the electric power generator for converting a voltage anda frequency of electric power generated by the electric power generatorinto a desired voltage and a desired frequency; a system collaborationunit between the motor and a commercial power source for changing asystem from the power source to a side of the motor or from the inverterto a side of the commercial power source; and a cable for connecting anelectric path between the system collaboration unit and the motor to anoutput port of the inverter.

[0012] <To Start Operation>

[0013] 1) Before operation, close a waterwheel inlet valve, a waterwheeloutlet valve, and a waterwheel bypass valve. First, turn on power of theheat source and power of the motor to drive the primary cool/warm pump.

[0014] 2) Next, transmit an operation request signal from the heatsource side to the primary cool/warm pump.

[0015] 3) The primary cool/warm pump receives the operation requestsignal transmitted from the heat source side to start its operation andsupply wager from the heat storage to the load side. Simultaneously, thepump transmits an operation answer signal to the heat source.

[0016] 4) After the operation answer signal is received, when apredetermined period of time lapses enough to guarantee a water supplypressure, the heat source starts its operation.

[0017] 5) When a predetermined period of time lapses after the heatsource starts its operation, the waterwheel outlet and inlet valves areopened. In association therewith, the waterwheel starts its operation.The rotation speed of the waterwheel increases with a lapse of time andthe electric power generator starts its operation.

[0018] 6) Generated power is supplied via the inverter to a load, forexample, the motor to drive the primary cool/warm pump. In anotherembodiment, the system collaboration unit is connected to a commercialpower source and there is provided a unit to connect an output from theinverter to an electric path between the system collaboration unit and aload. In this case, when the load is in a low state and the generatedpower is excessive, unused power is fed back via the systemcollaboration unit to the power source.

[0019] 7) The expansion tank or the vacuum breaking valve is disposed inan upper section of the water supply pipe and includes an atmosphericopening or a function similar to that of the atmospheric opening. Thetank or the valve prevents expansion of water in the water supply pipeand breaks a vacuum state by exhausting air from the pipe or by suckingexternal air therein to help the supplied water fall onto thewaterwheel.

[0020] In another embodiment, a pressure sensor disposed in the vicinityof the waterwheel senses pressure at the position. When the waterpressure becomes equal to or more than a predetermined value, anautomatic valve disposed in the vicinity of the waterwheel is opened.

[0021] <To Stop Operation>

[0022] 8) When a predetermined period of time lapses after the heatsource starts its operation, close the waterwheel outlet valve and stopthe waterwheel. Stop the electric power generator.

[0023] 9) Stop supplying the generated power, stop the inverter, stopsupplying power to the motor to drive the primary cool/warm pump.

[0024] 10) Transmit a stop request signal from the heat source side tothe primary cool/warm pump side.

[0025] 11) Receive the stop request signal, stop the motor to drive theprimary cool/warm pump, and return a stop answer signal to the heatsource.

[0026] 12) Interrupt the power to the motor to drive the primarycool/warm pump and interrupt the power to the heat source.

[0027] According to the present invention, there is provided an energycollecting system in a building, wherein a water pump on asecondary-side system to supply water to a group of air-conditioningloads is driven by an inverter, a waterwheel is operated by potentialenergy of water used by the air-conditioning loads, an electric powergenerator is operated by torque generated by the waterwheel, powergenerated by the electric power generator is converted by a regenerativeconverter into direct-current (dc) power, and positive-side dc power Pthereof and negative-side dc power N thereof are outputted to dcterminals P and N of an inverter for the water pump.

[0028] The system of the present invention is configured as above andoperates as follows.

[0029] 1) Before operation, the waterwheel inlet and outlet valves andthe waterwheel bypass valve are closed. First, the inverter to drive thewater pump in the secondary-side system is activated to operate thewater pump to supply water to air conditioners as air-conditioningloads. The inverter receives a sense signal from a pressure sensordisposed on the pump discharge side to conduct, for example, controloperation to fix a terminal pressure.

[0030] 2) The waterwheel starts its operation when the water havingpassed the respective air conditioners flows thereonto. The electricpower generator starts its operation by torque generated by thewaterwheel to generate electric power.

[0031] 3) The inverter on the electric power generator side convertspower (alternating current) generated by the electric power generatorinto dc power to supply the dc power to another inverter via a cable.

[0032] The present invention is not limited to a system or a facilityarranged in a building. That is, the configuration includes a heatstorage for storing water fed from a heat source, a heat source forproducing cool or warm water using water supplied from the heat storage,a pump for supplying the water from the heat storage to the heat source,a motor for driving the pump, a waterwheel rotated by the water suppliedfrom the heat source, an electric power generator driven by thewaterwheel for generating electric power, an inverter connected to anoutput port of the electric power generator, a system collaboration unitdisposed between the motor and a commercial power source for conductinga change-over operation between a system connecting the commercial powersource to the motor and a system connecting the inverter to thecommercial power source, and a connecting line for connecting anelectric path between the system collaboration unit and the motor to anoutput port of the inverter.

[0033] Other objects, features and advantages of the invention willbecome apparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034]FIG. 1 is a diagram showing a configuration of a first embodimentof the present invention,

[0035]FIG. 2 is a graph showing an operating characteristic of a pumpand a waterwheel of the first embodiment of the present invention,

[0036]FIG. 3 is a diagram showing a configuration of a second embodimentof the present invention,

[0037]FIG. 4 is a diagram showing a configuration of a third embodimentof the present invention,

[0038]FIG. 5 is a diagram showing a configuration of a fourth embodimentof the present invention,

[0039]FIG. 6 is a diagram showing a configuration of a fifth embodimentof the present invention,

[0040]FIG. 7 is a flowchart of a sixth embodiment of the presentinvention,

[0041]FIG. 8 is a flowchart of a seventh embodiment of the presentinvention,

[0042]FIG. 9 is a diagram showing a configuration of an eighthembodiment of the present invention,

[0043]FIG. 10 is a diagram showing an electric system of the eighthembodiment of the present invention,

[0044]FIG. 11 is a graph showing a characteristic of the eighthembodiment of the present invention,

[0045]FIG. 12 is a diagram showing a configuration of a system of theprior art, and

[0046]FIG. 13 is a graph showing an operating characteristic of a pumpand a waterwheel of the prior art.

DESCRIPTION OF THE EMBODIMENTS

[0047] Next, description will be given of an embodiment of the presentinvention by referring to FIGS. 1 to 11.

[0048]FIG. 1 shows a configuration of a first embodiment of the presentinvention. In this diagram, when compared with FIG. 9 showing a priorart example, the both-end motor is replaced with a general motor (anon-both-end motor), the water pump is separated from the waterwheel, anelectric power generator is disposed in the waterwheel (or an integraltype of these units is also available), and an inverter is connected toan output port of the electric power generator. A system collaborationunit 20 is disposed between a motor 2 to drive the water pump 1 and apower source 19. The system collaboration unit 20 is connected via acable 21 to the motor 2. Furthermore, an output of the inverter isconnected via a cable 14 a to the motor 2. When the waterwheel is notoperating, the system collaboration unit 20 operates to supply powerfrom a commercial power source 19 to the motor 2. When the waterwheel isoperating and power generated by the electric power generator 13 isinsufficient according to a load state of the water pump 1, the systemcollaboration unit 20 operates to supply power obtained by adding powerfrom the commercial power source to the power generated by the electricpower generator 13. When there remains unused power in the generatedpower, the unused power is returned from the inverter to the commercialpower source via the system collaboration unit. The units or devicesassigned with the same reference numerals are the same as those of FIG.9, and hence description thereof will be avoided.

[0049]FIG. 2 shows an operating characteristic of the pump and thewaterwheel of the first embodiment of the present invention. Thecomponents assigned with the same reference numerals are the same asthose of FIG. 10 and hence description thereof will be avoided. Inoperation of the first embodiment of the present invention, to obtainthe shaft power L1 for the water pump flow rate Q0, power L3 generatedby a combination of “waterwheel-electric power generator-inverter” andpower L2 from the commercial power source are used. In other words, aninsufficient power of the power generated by the waterwheel is suppliedfrom the commercial power source via the system collaboration unit.Naturally, when the opening of two-way valve is choked and the load onthe water pump is reduced, the electric power to drive the motor becomesless than the power generated by the waterwheel depending on cases. Inthis case, unused electric power is returned from the inverter via thesystem collaboration unit to the power source side. In the presentembodiment, the power collection ratio (L3/L1) is about 40% to about 60%and is improved when compared with the power collection ratio of theprior art.

[0050] Description will be given of a second embodiment by referring toFIG. 3. In the embodiment, as compared with the first embodiment, theload of the electric power generator is changed from the motor to drivethe primary cool/warm pump to the heat source. In FIG. 3, numeral 520 isa system collaboration unit disposed between the commercial power source18 and a power source terminal of the heat source 4. An output from theinverter 14 is connected via a cable 14 a to an electric path 521 of thesystem collaboration unit. That is, when the waterwheel is notoperating, the system collaboration unit 520 operates to supply powerfrom the commercial power source 18 to the heat source 4. When thewaterwheel is operating and if power generated by the electric powergenerator 13 is insufficient according to a load state of the heatsource 4, the system collaboration unit 520 operates to supply powerobtained by adding the power generated by the electric power generator13 to the power from the commercial power source 18. If there remainsunused power in the power generated by the power generator 13, theunused power is returned from the inverter via the system collaborationunit to the commercial power source.

[0051] Description will be given of a third embodiment by referring toFIG. 4. In this embodiment, power generated by the waterwheel issupplied to a group of various loads such as lighting apparatuses in abuilding. In FIG. 4, numeral 30 indicates a group of various loads suchas lighting apparatuses in a building and numeral 29 is a power systemchange-over unit. When the change-over unit 29 is set to a c-a side, thegroup of loads is connected to the commercial power source. When thechange-over unit 29 is set to a c-b side, the group of loads isconnected to the electric power generator side. That is, when thewaterwheel is operating and if the power generated by the electric powergenerator 13 is sufficient according to a load state of the group ofloads 30, the change-over unit 29 is set to a c-b side to supply powergenerated by the electric power generator 13. When the power generatedby the electric power generator 13 is insufficient, the change-over unit29 is set to a c-a side to supply power from the commercial powersource.

[0052] A fourth embodiment will be described by referring to FIG. 5. Inthis embodiment implemented by further modifying the third embodiment,when the group of loads imposes a high load and the power generated bythe electric power generator 13 is insufficient, the power from theelectric power generator 13 is added to that from the commercial powersource. In FIG. 5, as compared with FIG. 6, the group of loads 30 can bepowered from the electric power generator 13 and from the commercialpower source 28. An inverter 14 is connected to the electric powergenerator 13, a system collaboration unit 720 is connected between thecommercial power source 28 and the group of loads 30, and a cable 14 aconnects an electric path connecting the system collaboration unit 720to a power source terminal of the group of loads 30 to an output fromthe inverter.

[0053] In the configuration, when the generated power is insufficient,there is supplied power obtained by adding the generated power to thatfrom the commercial power source.

[0054] Description will now be given of a fifth embodiment by referringto FIG. 6. In the embodiment, a bypass pipe 29 a and a bypass valve 29are arranged to bypass valves before and after the waterwheel 12 and apressure gauge 31 a and a pressure sensor 31 are disposed on the inletside of the waterwheel and a pressure gauge 30 a and a pressure sensor30 are disposed on the outlet side of the waterwheel. In thisconfiguration, to maintain the waterwheel 12, the electric powergenerator 13, and units associated therewith, the gate valves 26 and 27are closed and the gate valve 29 is opened to return the water havingpassed the heat source to the heat storage via the water supply pipe 6a, the bypass pipe 29 a, and the valve 29 in this sequence. As a result,the heat source can be operated also during maintenance of thewaterwheel 12, the electric power generator 13, and units associatedtherewith.

[0055] Description will be given of a sixth embodiment by referring toFIG. 7. In the embodiment, although not shown, the operations andcontrol procedures are specified for the controller of the heat source,the motor to drive the primary cool/warm water pump, the electric powergenerator, the inverter, and the units as loads such that theseconstituent components collaboratively conduct operations. FIG. 7 showsthe operations and control procedures in a flowchart. That is, to startoperation, the inlet valve of the waterwheel is opened, the outlet valuethereof is closed, and the bypass valve thereof is closed in step 1. Instep 2, the heat source is powered. The motor to drive the primarycool/warm water pump is powered in step 3. In step 4, an operationrequest signal is transmitted from the heat source side to the primarycool/warm water pump. In step 5, the primary cool/warm water pumpreceives the operation request signal and operates the motor to drivethe primary cool/warm water pump. The pump then sends an operationanswer signal to the heat source. In step 6, when a predetermined periodof time lapses after the heat source receives the answer signalindicating the operation of the motor to drive the primary cool/warmwater pump, the heat source starts its operation. In step 7, when apredetermined period of time lapses after the heat source starts itsoperation, the waterwheel outlet valve is opened. As a result, thewaterwheel starts its operation and the electric power generator alsostarts its operation. In step 8, power generated by the electric powergenerator is supplied via the inverter to the primary cool/warm waterpump. Next, to stop operation, the waterwheel outlet valve is closed instep 9 to stop the waterwheel. This stops the electric power generator.

[0056] In step 10, the system stops supplying the generated power andstops the inverter. The system then stops supplying power to the motorto drive the primary cool/warm water pump. In step 10, a stop requestsignal is sent from the heat source side to the primary cool/warm waterpump side and the heat source stops its operation. In step 11, the motorto drive the primary cool/warm water pump receives the stop requestsignal and stops its operation. In step 12, the motor returns a stopanswer signal to the heat source. In addition, the system turns offpower to the motor and power to the heat source. In the description ofthe embodiment, the motor to drive the primary cool/warm water pump isused as an example of the load of the electric power generator. However,the load may be a heat source or another load such as a lightingapparatus in a building. By specifying the operations and the controlprocedures as above, the respective constituent components can beoperated in an appropriate collaborative fashion to achievepredetermined performance and functions without errors.

[0057] Description will now be given of a seventh embodiment byreferring to FIG. 8. The embodiment is implemented by further modifyingthe sixth embodiment to conduct an automatic and collaborativeoperation. Therefore, the gate valves 26, 27, and 29 of FIG. 6 aremodified to automatic valves. Although not shown, the operations andcontrol procedures are specified for the controller of the heat source,the motor to drive the primary cool/warm water pump, the electric powergenerator, the inverter, and the units as loads such that theseconstituent components automatically and mutually conduct operations ina collaborative way.

[0058]FIG. 8 shows the operations and the control procedures in aflowchart. To enable automatic operation, step 7 is added to FIG. 7 toopen the waterwheel outlet and inlet valves when the waterwheel inletpressure becomes equal to or more than a predetermined pressure toautomatically operate the waterwheel 12, the electric power generator13, and units associated therewith. In a phase to stop operation, step 9is similarly added to FIG. 7 to close the waterwheel outlet and inletvalves to automatically the waterwheel 12, the electric power generator13, and units associated therewith. The other operations are the same asthose of FIG. 7 and hence description thereof will be avoided. Throughthe operation, the operation management becomes easier without any riskof erroneous operations.

[0059] As a further improvement of the embodiment, the open controlcondition of the waterwheel inlet and outlet valves during the operationincludes that the heat source is operating and the inlet valve pressureis equal to or more than a predetermined pressure. When both conditionsare satisfied, the open control is carried out. As a result, theoperation is guaranteed and the overall system operates in acollaborative way.

[0060]FIG. 9 shows a configuration of a specific embodiment of thepresent invention. In this diagram, when compared with the prior artexample, the both-end motor 2 is replaced with a general motor 131 (anon-both-end motor) to separate the water pump 107 from the waterwheel109 in the secondary-side system to supply water to air-conditioningloads. An electric power generator 134 is disposed in the waterwheel 109(or an integral type of these units is also available). An inverter 135(INV2) is connected to an output port of the electric power generator134. Power generated by the power generator 134 is converted into a dcvoltage by the inverter 135 including semiconductor devices such as apower transistor Tr and a flywheel diode D. The power is then smoothedby a capacitor C. For example, when the ac voltage generated by theelectric power generator 134 is 200 V, the voltage (dc voltage) betweenthe P and N terminals of the inverter 135 is 280 V. The inverter 135 iswell known, for example, is an inverter using pulse width modulation(PWM) control and hence detailed description thereof will be avoided.The positive side P and the negative side N of the dc voltage outputfrom the inverter 135 are respectively connected to the positive side Pand the negative side N of a dc intermediate circuit of an inverter 136(INV1)to drive the motor 131. The inverter 136 is also well known andis, for example, an inverter using PWM control and hence detaileddescription thereof will be avoided.

[0061] In the system configured as above, when the air-conditioning loadvaries, the flow rate of water supplied to the waterwheel 109 inevitablyvaries and the power generated by the electric power generator 134 alsovaries. In this case, for example, each time the P-N voltage sensedbetween the terminals P and N as described above is lower than 280, ifthe operating frequency of the inverted 135 is lowered, a regenerativestate takes place and the P-N voltage increases although not shown inthe diagram.

[0062] The motor 131 to drive the water pump 107 is driven by theinverter 136. The inverter 136 is used because when the air-conditioningload varies, an energy saving operation is conducted by accordinglylowering the rotary speed of the pump. The dc voltage terminals P and Nof the inverter 135 are respectively connected to the dc voltageterminals P and N of the inverter 136 using cables 138 and 139,respectively. As a result, the power generated by the electric powergenerator 134 can be supplied using a direct current to the inverter 136on the water pump side. Therefore, it is not required to convert thepower into an alternating current, and a simple and inexpensiveconfiguration can be implemented without requiring a systemcollaboration unit.

[0063]FIG. 10 shows an electric system of FIG. 9. The constituentcomponents assigned with the same reference numerals are the same asthose shown in FIG. 1, and hence description thereof will be avoided. Inthe diagram, numeral 103 indicates a commercial power source, numeral132 is a wattmeter, and ELB indicates an electric leakage breaker. In aninitial state of operation, since the waterwheel 109 and the electricpower generator 134 are not operating, power is not supplied from the dcvoltage terminals P and N of the inverter 135. The water pump 107 andthe motor 131 are driven by the inverter 136 using power only from thecommercial power source 103. Water is supplied by the operation of thewater pump 107 to each air-conditioning load 110. When the water used bythe load returns to the waterwheel 109, the waterwheel 109 and theelectric power generator 134 start operation to supply dc power from theinverter 135 via the cables 138 and 139 to the dc voltage terminals Pand N of the inverter 136.

[0064]FIG. 11 shows a graph of an operating characteristic of the waterpump 107 and the waterwheel 109 in the embodiment of the presentinvention. In this case, the water pump 107 is controlled by theinverter 136 to keep a terminal pressure at a fixed value (the rotaryspeed of the pump is controlled to keep the terminal pressure of thepipe at a fixed value such that a pump discharge pressure is on a piperesistance curve E). The items assigned with the same reference numeralsare the same as those of FIG. 5, and hence description thereof will beavoided. In the embodiment of the present invention, to obtain shaftpower L1 at a flow rate of Q₀ by operating the water pump 107 with ahighest frequency of Nmax of the inverter 136, there is used powerobtained by adding power L3 generated by a combination of the waterwheel109, the electric power generator 134, and the inverter 135 tomechanical power (electric power) L2 from the commercial power source.In other words, power insufficient in the power generated by thewaterwheel is supplied from the commercial power source 103. Naturally,when the air-conditioning load is decreased and the load of the waterpump 107 is lowered and the flow rate becomes Q₁, the water pump 107 isoperated with a frequency of N₁, of the inverter 136 and has performanceon the curve F. The shaft power is indicated by a curve I₂ and theoperation points are respectively O₄ and O₄′. When the flow rate becomeszero, the inverter 136 is operated by a frequency of N₂, and the waterpump 107 has performance on a curve G. The shaft power is indicated by acurve I₃ and the operation points are respectively O₆ and O₆′. When thewaterwheel 109 is not operated, the operation is conducted on a curve Lconnecting the points O₁, O₄, and O₆ of the shaft power. In operation ofthe waterwheel 109, when water flows onto the waterwheel 109 at a flowrate of Q₀, there appears a head H₀ between the inlet and the outlet ofthe waterwheel. Therefore, the waterwheel generates torque usingpotential energy of the water, and power is generated by the electricpower generator 134 corresponding to shaft power L3. In subsequentoperation, when the water flow rate varies, power is generated inaccordance with the variation in a similar way. When the water pump 107,the waterwheel 109, and the electric power generator 134 aresimultaneously operated, a curve L4 is obtained. The power supplied fromthe commercial power source 103 is reduced as much as there is powergenerated by the electric power generator 134. Point O₃ in the diagramindicates a point at which the waterwheel 109 is efficiently operated bya flow rate of Q₃ and the electric power generator 134 generateselectric power.

[0065] In the embodiment, the power collection ratio (L3/L1) is about40% to about 60% and is improved as compared with the collection ratioof the prior art. In the embodiment, the power generated by the electricpower generator 134 is converted by the inverter 135 into a directcurrent to be supplied to the terminals P and N of the inverter 136 todrive the water pump 107 in a building. However, if the load is drivenby an inverter, the power can be supplied not only to the inverter 136,but may also be supplied to any inverter of another facility. Since theterminals P and N of the inverter 135 are connected to the terminals Pand N of the inverter 136 using a cable, when the cable becomes long,wiring loss is increased. Both inverters may be collectively arranged inone control board. As a result, the wiring loss can be improved.

[0066] As above, when compared with the unused energy collectingapparatus of the prior art using a waterwheel, there is obtained effectof further improvement the collection ratio according to the presentinvention. Since the present invention can cope with various loads,unused energy of a building can be efficiently re-used.

[0067] Since the power generated by the electric power generator issupplied as dc power via an inverter to another inverter, the power isnot converted into an alternating current. Therefore, a simple andinexpensive system can be constructed without requiring a systemcollaboration unit.

[0068] It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. An energy collecting system, comprising: a heat storage; a heatsource for imparting heat to water supplied from the heat storage byelectric power from a commercial power source and thereby producing coolor warm water; a primary cool/warm water pump for pumping up the waterfrom the heat storage and supplying the water via a sucking pipe to theheat source; a motor for driving the primary cool/warm water pump; awater supply pipe disposed between a discharge outlet of the primarycool/warm water pump and the heat source; a water supply pipe forreturning water from a discharge outlet of the heat source to the heatstorage; an expansion tank or a vacuum breaking valve disposed in ahighest section of the water supply pipe; a waterwheel disposed in alowest section of the water supply pipe for collecting potential energyof the water discharged from the heat source; and an electric powergenerator rotated by torque generated by the waterwheel to generateelectric power.
 2. An energy collecting system according to claim 1,comprising: an inverter connected to an output port of the electricpower generator for converting a voltage and a frequency of electricpower generated by the electric power generator into a desired voltageand a desired frequency; a system collaboration unit between the motorand a commercial power source for changing a system from the commercialpower source to a side of the motor or from the inverter to a side ofthe commercial power source; and a cable for connecting an electric pathbetween the system collaboration unit and the motor to an output port ofthe inverter.
 3. An energy collecting system according to claim 1,comprising: an inverter connected to an output port of the electricpower generator for converting a voltage and a frequency of electricpower generated by the electric power generator into a desired voltageand a desired frequency; a system collaboration unit between the motorand a commercial power source for changing a system from the commercialpower source to a side of the motor or from the inverter to a side ofthe commercial power source; and a cable for connecting an electric pathbetween the system collaboration unit and the motor to an output port ofthe inverter, wherein the motor to drive the primary cool/warm waterpump is driven by electric power obtained by adding the power generatedby the waterwheel to the power of the commercial power source.
 4. Anenergy collecting system according to claim 1, comprising: an inverterconnected to an output port of the electric power generator forconverting a voltage and a frequency of electric power generated by theelectric power generator into a desired voltage and a desired frequency;a system collaboration unit between the heat source and a commercialpower source for changing a system from the commercial power source to aside of the heat source or from the inverter to a side of the commercialpower source; and a cable for connecting an electric path between thesystem collaboration unit and the heat source to an output port of theinverter.
 5. An energy collecting system according to claim 1,comprising: an inverter connected to an output port of the electricpower generator for converting a voltage and a frequency of electricpower generated by the electric power generator into a desired voltageand a desired frequency; a system collaboration unit between the heatsource and a commercial power source for changing a system from thecommercial power source to a side of the heat source or from theinverter to a side of the commercial power source; and a cable forconnecting an electric path between the system collaboration unit andthe heat source to an output port of the inverter, wherein the heatsource is driven by electric power obtained by adding the powergenerated by the waterwheel to the power of the commercial power source.6. An energy collecting system according to claim 1, wherein theelectric power generated by the electric power generator is supplied toa load such as a lighting apparatus in a machine room.
 7. An energycollecting system according to claim 1, comprising an electric powerchange-over unit for changing a system, when power is not beinggenerated, from a commercial power source to a load side and forchanging the system, when power is being generated, from the electricpower generator to a load side, wherein the electric power generated bythe electric power generator is supplied to a load such as a lightingapparatus in a machine room.
 8. An energy collecting system according toclaim 1, comprising: an inverter for converting the generated electricpower desired by a load connected to an output port of the electricpower generator into a voltage and a frequency; a system collaborationunit between the load and a commercial power source for changing asystem from the commercial power source to a side of the load or fromthe inverter to a side of the commercial power source; and a cable forconnecting an electric path between the system collaboration unit andthe load to an output port of the inverter.
 9. An energy collectingsystem according to one of claim 1, comprising: a bypass pipe and abypass valve bypassing the waterwheel; and pressure sensors disposed atan inlet and an output of the waterwheel.
 10. A method of operating anenergy collecting system comprising: a heat storage; a heat source forimparting heat to water supplied from the heat storage by electric powerfrom a commercial power source and thereby producing cool or warm water;a commercial power source for supplying electric power to the heatsource; a primary cool/warm water pump for pumping up the water from theheat storage and supplying the water via a sucking pipe to the heatsource; a motor for driving the primary cool/warm water pump; a watersupply pipe disposed between a discharge outlet of the primary cool/warmwater pump and the heat source; a water supply pipe for returning waterfrom a discharge outlet of the heat source to the heat storage; anexpansion tank or a vacuum breaking valve disposed in a highest sectionof the water supply pipe; a waterwheel disposed in a lowest section ofthe water supply pipe for collecting potential energy of the waterdischarged from the heat source; an electric power generator rotated bytorque generated by the waterwheel to generate electric power; and aninverter connected to an output port of the electric power generator,the inverter converting the generated electric power desired by a loadside into a voltage and a frequency and supplying the power to the motorto drive the primary cool/warm water pump, wherein the respective unitscollaboratively operate according to steps below: <To StartOperation>
 1. Open a waterwheel inlet valve, close a waterwheel outletvalve, and close a waterwheel bypass valve.
 2. Power the heat source. 3.Power the motor to drive the primary cool/warm pump.
 4. Transmit arequest signal from the heat source side to operate the primarycool/warm pump.
 5. Receive the operation request signal, operate themotor to drive the primary cool/warm pump, and transmit an operationanswer signal to the heat source.
 6. Operate the heat source when apredetermined period of time lapses after the operation answer signal isreceived.
 7. When a predetermined period of time lapses after the heatsource is operated, close the waterwheel outlet valve and operate thewaterwheel. Operate the electric power generator.
 8. Supply generatedelectric power via the inverter to the motor to drive the primarycool/warm pump. <To Stop Operation>
 1. Close the waterwheel outlet valveand stop the waterwheel. Stop the electric power generator.
 2. Stopsupplying the generated power, stop the inverter, stop supplying powerto the motor to drive the primary cool/warm pump.
 3. Transmit a stoprequest signal from the heat source side to the primary cool/warm pumpside. Stop the heat source.
 4. Receive the stop request signal, stop themotor to drive the primary cool/warm pump, and return a stop answersignal to the heat source.
 5. Interrupt the power to the motor to drivethe primary cool/warm pump and interrupt the power to the heat source.11. A method of operating an energy collecting system comprising: a heatstorage; a heat source for imparting heat to water supplied from theheat storage by electric power from a commercial power source andthereby producing cool or warm water; a commercial power source forsupplying electric power to the heat source; a primary cool/warm waterpump for pumping up the water from the heat storage and supplying thewater via a sucking pipe to the heat source; a motor for driving theprimary cool/warm water pump; a water supply pipe disposed between adischarge outlet of the primary cool/warm water pump and the heatsource; a water supply pipe for returning water from a discharge outletof the heat source to the heat storage; an expansion tank or a vacuumbreaking valve disposed in a highest section of the water supply pipe; awaterwheel disposed in a lowest section of the water supply pipe forcollecting potential energy of the water discharged from the heatsource; an automatic valve disposed to bypass the waterwheel; anautomatic valve disposed in the an inlet or outlet of the waterwheel;pressure sensors disposed in the outlet and the inlet of the waterwheel;an electric power generator rotated by torque generated by thewaterwheel to generate electric power; and an inverter connected to anoutput port of the electric power generator, the inverter converting thegenerated electric power desired by a load side into a voltage and afrequency and supplying the power to the motor to drive the primarycool/warm water pump, wherein the respective units automatically andcollaboratively operate according to steps below: <To StartOperation>
 1. Close the waterwheel bypass valve.
 2. Power the heatsource.
 3. Power the motor to drive the primary cool/warm pump. 4.Transmit a request signal from the heat source side to operate theprimary cool/warm pump.
 5. Receive the operation request signal, operatethe motor to drive the primary cool/warm pump, and transmit an operationanswer signal to the heat source.
 6. Operate the heat source when apredetermined period of time lapses after the operation answer signal isreceived.
 7. When pressure at the waterwheel inlet reaches predeterminedpressure, the automatic valves in the outlet of the waterwheel open andthe waterwheel operates. The electric power generator operates inassociation therewith.
 8. Supply generated electric power via theinverter to the motor to drive the primary cool/warm pump. <To StopOperation>
 9. When a predetermined period lapses after the heat sourceis operated, close the automatic outlet and inlet valves of thewaterwheel and stop the waterwheel. Stop the electric power generator.10. Stop supplying the generated power, stop the inverter, stopsupplying power to the motor to drive the primary cool/warm pump. 11.Transmit a stop request signal from the heat source side to the primarycool/warm pump side.
 12. Receive the stop request signal, stop the motorto drive the primary cool/warm pump, and return a stop answer signal tothe heat source.
 13. Interrupt the power to the motor to drive theprimary cool/warm pump and interrupt the power to the heat source.
 12. Amethod of operating an energy collecting system according to claim 10,comprising a step of completely opening the automatic valves in thewaterwheel outlet and inlet when the heat source operates and thepressure sensor in the waterwheel inlet senses the predeterminedpressure.
 13. An energy collecting system, wherein: a water pump tosupply water to a group of air-conditioning loads is driven by aninverter; a waterwheel is operated by potential energy of water used bythe air-conditioning loads; an electric power generator is operated bytorque generated by the waterwheel; and power generated by the electricpower generator is converted by an inverter into direct-current (dc)power.
 14. An energy collecting system according to claim 13, whereinthe dc power is returned as dc power of the inverter.
 15. An energycollecting system according to claim 13, whereinthe dc power is returnedas dc power of an inverter other than the inverter.
 16. An energycollecting apparatus, comprising: a heat storage; a water pump of asecondary system for pumping up water from the heat storage andsupplying the water to a group of air-conditioning loads; a firstinverter for driving the water pump; a first water supply pipe disposedbetween a discharge outlet of the water pump and the group ofair-conditioning loads; a second water supply pipe for returning waterdischarged from a discharge outlet of the group of air-conditioningloads to the heat storage; an expansion tank or a vacuum breaking valvedisposed in a highest section of the second water supply pipe; awaterwheel disposed in a lower section of the second water supply pipefor collecting potential energy of the water discharged from the groupof air-conditioning loads; and an electric power generator rotated bytorque generated by the waterwheel to generate electric power.
 17. Anenergy collecting apparatus according to claim 16, comprising: a secondinverter connected to an output port of the electric power generator togenerate dc power; and means for connecting the first inverter to a dcsection of the second inverter, wherein the dc power generated by thesecond inverter is returned to the first inverter.
 18. An energycollecting apparatus according to claim 16, comprising: a secondinverter connected to an output port of the electric power generator togenerate dc power; and means for connecting a dc section of the secondinverter to an inverter other than the second inverter, wherein the dcpower generated by the second inverter is returned to the inverter otherthan the second inverter.
 19. An energy collecting apparatus accordingto one of claim 16, wherein the first and second inverters areincorporated in a control board.
 20. An energy collecting system,comprising: a heat storage for storing therein water obtained from aheat source; a heat source for producing cool or warm water using waterfrom the heat storage; a pump for supplying the water from the heatstorage to the heat source; a motor for driving the pump; a waterwheelrotated by the water supplied from the heat source; an electric powergenerator driven by the waterwheel to generate electric power; aninverter connected to an output port of the electric power generator; asystem collaboration unit disposed between the motor and a commercialpower source, the system collaboration unit conducting a change-overoperation between a system connecting the commercial power source to themotor and a system connecting the inverter to the commercial powersource; and a connecting line for connecting an electric path betweenthe system collaboration unit and the motor to an output port of theinverter.